“Diogo is an extremely talented young defender with all the qualities to quickly become a great player for this club,” Mourinho told the club’s official website.

“He has all the attributes that a full-back needs: physicality, tactical intelligence and technical quality, combined with a Porto Academy mentality which prepares players for the maturity they need at the professional level.

“In his age group, he is the best full-back in Europe and we all believe he has a bright future ahead of him at Manchester United.”

Dalot added: “Joining Manchester United is an unbelievable opportunity for me. I have grown up in Porto’s Academy and I am so thankful for everything they have done for me.

“But the chance of coming to the biggest club in the world is something I just couldn’t turn down. I’m excited about working with Jose Mourinho and learning everything I can from such a successful coach.

“I am looking forward to playing alongside the fantastic players in the squad.”